Composite ophthalmic microcannula

ABSTRACT

Microcannulae are constructed with multiple components in a composite design, allowing the microcannulae to have varying mechanical and delivery properties that will enable ophthalmic treatments by minimally invasive means. The microcannula includes at least one flexible, tubular communicating element with an outer diameter of 350 microns or less, a proximal connector for introduction of materials, energy or tools. It may also include a reinforcing member attached to the communicating element, which may be designed to create variable stiffness along the length of the microcannula. The microcannula may also include other features such as a signal beacon near the distal tip.

CROSS-REFERENCE TO OTHER APPLICATIONS

This application is a continuation of U.S. utility patent applicationSer. No. 11/042,825, filed Jan. 24, 2005, which claims the benefit ofU.S. provisional patent application Ser. No. 60/538,625, filed Jan. 23,2004, the disclosures of which are hereby incorporated by reference intheir entirety.

FIELD OF THE INVENTION

The present invention relates to microcannulae that are constructed withmultiple components in a composite design. The composite design allowsthe microcannula to have varying mechanical and delivery properties thatwill enable ophthalmic treatments by minimally invasive means.

BACKGROUND OF INVENTION

A variety of catheters and cannulae are used in ophthalmic surgery todeliver fluid, gas, suction and energy to select regions of the eye.Existing cannulae are typically straight or curved segments of rigidplastic or metal tubing attached to a connector. In the development ofadvanced surgical methods to treat the eye, it is desired to havecannulae that can access and be advanced into very small structures orchannels in the eye to perform minimally invasive procedures. Suchmicrocannulae that access curved or tortuous spaces such as Schlemm'sCanal or small blood vessels require a combination of flexibility and“pushability”, while maintaining a diameter in the range of 50 to 350microns. The present invention describes microcannulae that areconstructed with multiple components in a composite design. Thecomposite design allows the microcannula to have varying mechanical anddelivery properties that will enable ophthalmic treatments by minimallyinvasive means.

PRIOR ART

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Method and apparatus to improve the outflow of the aqueous humor of aneye

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Ophthalmic Microsurgical Instruments

SUMMARY OF THE INVENTION

A composite microcannula for access and advancement into a tissue spaceof the eye comprising at least one flexible, tubular communicatingelement with an outer diameter of 350 microns or less, with proximal anddistal ends, and sized to fit within the tissue space; a proximalconnector for introduction of materials, energy and tools; and areinforcing member in conjunction with the communicating element.

A microcannula having a reinforcing member that provides for greateraxial and flexural stiffness at the proximal end of the microcannula andlower axial and flexural stiffness to the distal end.

A microcannula having a reinforcing element formed of metal.

A microcannula having a communicating element formed of a flexiblepolymer and a reinforcing member formed of metal.

A microcannula having two or more communicating elements.

A microcannula having communicating elements in concentric alignment.

A microcannula having communicating elements in parallel alignment

A microcannula comprising two communicating elements where the secondcommunicating element is located within the lumen of the firstcommunicating element.

A microcannula having two or more reinforcing elements.

A microcannula having a reinforcing element in the form of a coil.

A microcannula having a reinforcing element that is tapered toward thedistal end of the microcannula.

A microcannula having a communicating element formed of a segment oftubing, optical fiber or an electrical conductor.

A microcannula designed to fit within a tissue space such as Schlemm'sCanal, an aqueous collector channel, aqueous vein, suprachoroidal spaceor retinal blood vessel of the eye.

A microcannula having a distal tip with a rounded leading edge.

A microcannula having a communicating element and a reinforcing elementthat are joined by an outer sheath.

A microcannula having an outer sheath formed of heat shrink tubing.

A microcannula having an outer sheath that is thermally fused to thecommunicating element(s).

A microcannula having a communicating element and a reinforcing elementthat are joined with an adhesive.

A microcannula having a communicating element and a reinforcing elementthat are bonded through non-adhesive means such as thermal or ultrasonicwelding.

A composite microcannula for access and advancement into a tissue spaceof the eye comprising at least one flexible, tubular communicatingelement with an outer diameter of 350 microns or less, with proximal anddistal ends, to fit within the tissue space; and a coiled metalreinforcing member attached to the communicating element; wherein thecommunicating element is formed of a flexible polymer or a superelasticmetal alloy.

A composite microcannula for access and advancement into a tissue spaceof the eye comprising at least one flexible, tubular communicatingelement with an outer diameter of 350 microns or less, with proximal anddistal ends, and a fluid communicating lumen sized to fit within thetissue space; a proximal connector for introduction of fluid and asecond communicating element comprising an optical fiber, where themicrocannula provides means for the delivery of both fluid and a visiblelight signal to the distal tip of the microcannula simultaneously.

A composite microcannula for access and advancement into a tissue spaceof the eye comprising at least one flexible, tubular communicatingelement with an outer diameter of 350 microns or less, with proximal anddistal ends, and a fluid communicating lumen sized to fit within thetissue space; a proximal connector for introduction of fluid and asecond communicating element comprising an optical fiber, where themicrocannula has a rounded distal tip and provides means for thedelivery of both fluid and a visible light signal to the distal tip ofthe microcannula simultaneously.

A composite microcannula for access and advancement into a tissue spaceof the eye comprising at least one flexible, tubular communicatingelement with an outer diameter of 350 microns or less, with proximal anddistal ends, and a fluid communicating lumen sized to fit within thetissue space; a proximal connector for introduction of fluid, a secondcommunicating element comprising an optical fiber, and a reinforcingmember, where the microcannula provides means for the delivery of bothfluid and a visible light signal at the distal tip of the microcannulasimultaneously.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a composite microcannula having atapered reinforcing element.

FIG. 2 is a cross-sectional view of a composite microcannula having tworeinforcing elements, one full length and one partial length.

FIG. 3 is a part cross-sectional view of a composite microcannula havinga spiral wound reinforcing element in the form of a round wire.

FIG. 4 is a part cross-sectional view of a composite microcannula havinga spiral wound reinforcing element in the form of a flat ribbon.

FIG. 5 is a side view and close up view of a curved compositemicrocannula having a signaling beacon tip extending beyond the distaltip of outer sheath.

FIG. 6 is a cross-sectional view of a composite microcannula having atapered reinforcing element and a rounded distal tip.

FIG. 7 is a cross-sectional view of a composite microcannula having aball-end distal tip formed separately from the communicating element andan optical fiber to provide for a beacon with light dispersed at thetip.

DESCRIPTION OF INVENTION

The invention comprises a microcannula designed to be advanced into verysmall tissue spaces during surgery. In particular for ophthalmicsurgery, the microcannula may be used to cannulate Schlemm's Canal,aqueous humor collector channels, aqueous veins, retinal veins and thesuprachoroidal space. Such structures range from 50 to 250 microns indiameter, thereby restricting the outer diameter of the microcannula tosimilar dimensions. The microcannula comprises a flexible elongatedelement with a connector at the proximal end 3, a distal tip, and acommunicating channel 1 therebetween, as seen in FIG. 1. Thecommunicating channel 1 of the microcannula may be used to deliverfluids, materials, energy, gases, suction, surgical tools and implantsto a distal surgical site for a variety of surgical tasks. Thecommunicating channel 1 may be the lumen of a tube-like elongatedelement to transport materials, an optical fiber to transport lightenergy, or a wire to transport electrical signals. The flexibleelongated element with a communicating channel 1 is referred to as thecommunicating element. A single communicating element may have more thanone communicating channel.

The microcannula of the present invention incorporates specific designfeatures that enable it to be placed into very small tissue spaces. Akey feature is the use of a composite microcannula design that has theappropriate combination of axial stiffness and compliance. Themicrocannula is desired to be flexible to allow it to be advanced alonga curved or tortuous tissue space with minimal tissue trauma, but withsufficient axial stiffness or “pushability” to allow transfer of forceto advance the microcannula. For a fixed outer dimension, the mechanicalproperties of the microcannula may be tailored by the selection ofmaterials of construction and cross-sectional dimensions. In oneembodiment, a reinforcing element 2 is attached to the outside of acommunicating element. Typically, the reinforcing element 2 comprises amaterial with higher flexural modulus than the communicating element.The communicating element may be a thin wall polymer or metallic tube.The reinforcing element 2 may be formed of any high modulus materialsuch as, but not limited to, metals including stainless steel and nickeltitanium alloys, ceramic fibers and high modulus polymers, filled orreinforced polymers, and polymer-polymer composites.

For optimal use in small tissue spaces, the microcannula is desired tobe flexible at the distal tip, but transitioning to more rigidmechanical properties toward the proximal end. The transition maycomprise one or more steps in mechanical compliance, or a gradient ofcompliance along the length of the microcannula. The transition inmechanical properties may be accomplished by a change in thecross-sectional area or material properties of the microcannula alongits length, the incorporation of one or more stiffening members, or acombination thereof. In one embodiment of the invention, themicrocannula incorporates a communicating element 1 forming thecommunicating channel 1 fabricated from a flexible polymer with tworeinforcing members 4, 5 attached along the length, as seen in FIG. 2.One of the reinforcing members 5 extends along the communicating elementbut not completely to the distal tip, while the other reinforcing member4 extends completely to the distal tip to provide a transition inflexural compliance. The reinforcing members 4, 5 may be formed of ahigh modulus polymer or metal. In a similar embodiment, a singlereinforcing member with a transition in flexural stiffness, such as atapered wire 2, may be used to reinforce the communicating element.Alternatively, a reinforcing member may be formed of sequential segmentsof varying modulus or cross-sectional dimensions. The reinforcingelements may be held in place by an outer sheath 6 which may comprise atight fitting polymer tube or polymer shrink tubing. Alternatively, thereinforcing elements may be adhered or bonded to the communicatingelement, or may be fully or partially contained within the communicatingelement.

The reinforcing element may also provide kink resistance to thecommunicating element. This is especially advantageous for use withcommunicating elements fabricated from high modulus polymers, such aspolyimide, polysulfone, ultra-high molecular weight polyethylene andfiber reinforced polymer composites, which kink or deform under highloads, forming a permanent mechanical defect. The reinforcing elementmay also comprise a malleable material to allow the shape of themicrocannula to be adjusted manually to better accommodate a curvedshape of the tissue space. Possible malleable materials for thereinforcing element include but are not limited to steel, silver andplatinum alloys.

The reinforcement of the communicating element may also be accomplishedby the incorporation of coil-like members to provide high flexuralcompliance but also high axial stiffness for pushability, as seen inFIGS. 3 & 4. A reinforcing member 7, 8 attached to an outer sheath maybe a coiled or wound element on or formed into the exterior surface ofthe sheath. The reinforcing member 7, 8 may be any suitable high modulusmaterial including metals such as, but not limited to, stainless steel,titanium and superelastic alloys, ceramics such as ceramic fibers, andhigh modulus polymers or composite polymer structures such as carbonfiber reinforced epoxy. The members may have any suitable cross-sectionsuch as round or semi-circular 7 or rectangular 8, as in the case of aflat wire winding. The winding pitch of the reinforcing members may beconstant, or it may be varied to achieve differential flexuralproperties along the length of the microcannula. Multiple wound elementsmay be incorporated, with the elements being formed of like or differentmaterials. The reinforcing element or multiple reinforcing elements mayalso be configured to provide a preferred deflection orientation of themicrocannula.

The composite microcannula of the present invention may also includemultiple communicating elements. In one embodiment, the microcannula mayinclude two or more elongated communicating elements with a reinforcingmember to form a composite structure. The components may be adheredtogether, placed within an outer sheath, such as heat shrink tubing oran outer communicating element may contain one or more othercommunicating elements. One of the communicating elements may be usedfor transport of materials, another for transport of light or energy,thus providing a multifunctional surgical tool. The communicatingelements may be aligned side-by-side or arranged around one or morereinforcing elements. In one embodiment, one communicating element withan annular cross-section forming a lumen may be fitted with a secondcommunicating element within the lumen. Such concentric alignment ofcommunicating elements may also be used in combination with othercommunicating elements that are not in concentric alignment.

In one particular embodiment, the composite microcannula may be usedonly to transfer mechanical energy. For example, the microcannula may beused to advance into a tissue space and used to snare a foreign objector area of tissue. In such cases, the elongated communicating elementmay be a material such as a wire, polymer, or fiber composite ofappropriate mechanical properties. An inner member, which fits andslides within the communicating element, may also be incorporated, theinner member having at least a proximal end and a distal tip.Advancement or withdrawal of the inner member may be used to change theshape of the distal tip of the microcannula, or alternatively to effecta mechanical action at the distal tip.

In one embodiment, the microcannula also comprises a proximal connectorfor the communicating element. The connector may serve to connect asupply of material or energy, such as an infusion syringe or lightsource to the communicating channel 1 of the communicating element.Additionally, the microcannula may contain a central section comprisinga single or multiple side connectors to allow the attachment ofancillary equipment such as syringes, vacuum or pressure sources,sensing means and the like. The attachment connectors may use standarddesigns such as Luer fittings or may be designed to only acceptconnection with specific components. In another embodiment, thecomposite microcannula may incorporate fenestrations or windows alongthe length. The fenestrations may be used to deliver materials from thesides of the microcannula, for instance the delivery of therapeuticagents to the tissues of Schlemm's Canal. Alternately, with theconnection of a vacuum generating device to the proximal connector ofthe communicating element, the fenestrations may be used to providesuction against soft tissues. The suction may be used for the removal oftissue or may be used to anchor the microcannula in place while anotherelement is advanced through the microcannula. For example, a compositesuction microcannula may be used to strip the juxtacanicular tissuesfrom the inner wall of Schlemm's Canal.

The communicating element may be formed of a thin walled polymer ormetallic tube of sufficient stiffness to allow it to be advanced intotissues or along a tissue space such as Schlemm's Canal, and ofsufficient flexibility to follow the circular tract of Schlemm's Canal.Due to the small size of the target tissue spaces, the microcannula mustbe appropriately sized. Typically, the microcannula is sized in therange of 50 to 350 microns outer diameter with a wall thickness from10-100 microns. The cross-section of the microcannula may be round oroval or other bound shape to approximate the shape of a tissue spacesuch as Schlemm's Canal. In some embodiments, a predetermined curvaturemay be applied to the device during fabrication.

Suitable materials for the communicating element include metals,polyetheretherketone (PEEK), polyethylene, polypropylene, polyimide,polyamide, polysulfone, polyether block amide (PEBAX), fluoropolymers orsimilar materials. The outer sheath may also have surface treatmentssuch as lubricious coatings to assist in tissue penetration andultrasound or light interactive coatings to aid in location andguidance. The microcannula may also have markings on the exterior forassessment of depth in the tissue space. For example, the markings maytake the form of rings around the outer shaft located at regularintervals along the length of the microcannula. The external markingsallow user assessment of the length of the tissue space or channelaccessed by the microcannula, and the approximate location of themicrocannula tip.

In an embodiment of the invention, a first communicating element usedfor initial placement of the microcannula has a signaling beacon toidentify the location of the microcannula distal tip relative to thetarget tissues, as seen in FIG. 5. The signaling means may comprise anechogenic material for ultrasound guidance, an optically active materialfor optical guidance or a light source for visual guidance placed at themicrocannula tip or placed to indicate the position of the microcannulatip. In one embodiment, a plastic optical fiber (POF) 9 is used as acommunicating element to provide a bright visual light source at thedistal tip 10. The distal tip 10 of the POF 9 is positioned proximal to,near or slightly beyond the distal end of the microcannula sheath andthe emitted signal may be detected through tissues visually or usingsensing means such as infrared imaging. The POF 9 may also have a tipthat is beveled, mirrored or otherwise configured to provide for adirectional beacon. The beacon may be illuminated by a laser, laserdiode, light-emitting diode, or an incandescent source such as a mercuryhalogen lamp. In an alternate embodiment, the signaling means maycomprise visualization aids along the length of the microcannula, forexample a side emitting optical fiber of discrete length leading up tothe distal end or at a known point along the microcannula may be used toindicate the position of the microcannula and the distal tip. Uponplacement of the microcannula at the target tissues, the beacon assembly11 and POF 9 may be removed. The connection point may be sealed with acap or with a self-sealing mechanism such as a one-way valve or anelastomer seal. Alternatively, the POF may be placed co-linear to orwithin the lumen of a delivery communicating channel, allowing fordelivery of fluids or gases through the delivery communicating channelwithout requiring removal of the beacon assembly.

Alternate embodiments of the microcannula may use other imagingtechnologies to locate the signal beacon. Other possible imagingtechnologies include but are not limited to magnetic resonance imaging,fluoroscopy and ultrasound. In these embodiments, the beacon signal maytake other forms to match the imaging technology such as a radiopaquemarker attached to or embedded at or near the distal tip of themicrocannula. Alternatively or in addition, an echogenic material orcoating may be added to the distal tip, etc.

It is also preferred for the microcannula to have a rounded distal tip12 to minimize tissue trauma and aid the ability of the microcannula tobe advanced into small tissue spaces, as seen in FIGS. 6 and 7. Therounded tip 12 may be the same outer diameter as the microcannula orlarger, depending on the specific properties desired. The rounded tip 12may be formed and attached to the microcannula during assembly oralternatively, the microcannula tip may be processed by a secondaryoperation to form a rounded contour. When the rounded tip 12 is used inconjunction with a light emitting signaling beacon 9 such that the lightis delivered proximal to the rounded tip, the tip acts to disperse thelight 13. The dispersed light aids visualization when viewing themicrocannula off axis, for example when advancing the microcannula inSchlemm's Canal.

Another key feature of the invention is the use of a communicatingelement to deliver fluid to the distal tip during advancement of themicrocannula within the tissue space. The injection of small amounts offluid may serve to open the tissue space ahead of the microcannula tipand lubricate the channel to greatly increase the ability to advance themicrocannula atraumatically. Delivery of surgical viscoelastic materialssuch as hyaluronic acid solutions and gels are especially efficacious inaiding advancement and placement of the microcannula. Delivery offluids, especially gel-like viscoelastic materials, allows for thedilation of the tissue space in the circumstance that a constriction orpartial blockage is reached during advancement of the microcannula. Aparticularly effective embodiment comprises a microcannula with acommunicating element such as an optical fiber to provide a signalingbeacon at the microcannula tip and a second communicating element todeliver a fluid such as a solution of hyaluronic acid to themicrocannula tip while the signaling beacon is active. Such amicrocannula may be manually manipulated and used to deliver fluids toaid microcannula advancement while simultaneously observing themicrocannula tip location along the tissue space. The combination offluid delivery in the path of the microcannula and the observation ofthe microcannula tip when advanced, retracted and torsioned allowsprecisely controlled manipulation and advancement in tight tissuespaces. The ease of manipulation is further aided with the addition of areinforcing member to the communicating element of the microcannula.

EXAMPLES Example 1

In the following example, a composite microcannula with twocommunicating elements was fabricated. A communicating element with alumen (Polyimide Tubing 0.003 inch ID×0.004 inch OD), a secondcommunicating element comprising a plastic optical fiber (85-100microns, 0.0034-0.0039 inch OD), a reinforcement element (304SS wireground to 0.001 inches in the distal 2.5 inches tapering up over a 1.0inch length to a diameter of 0.003 inches for the remaining length ofthe microcannula), and an outer sheath comprising polyethyleneteraphthalate (PET) shrink tubing (0.008 inch ID and 0.00025 inch wallthickness), were all cut to lengths appropriate for setting the finaloverall length of the microcannula. The distal ends of the innercomponents were then aligned flush and joined with an adhesive. Thereinforcing element was tapered and aligned to provide more flexibilitydistally and stiffer reinforcement more proximal in the microcannula.The three elements were aligned in a triangular pattern rather than anin-line pattern to create an assembled profile with the smallestmajor-axis dimension. The assembly of multiple components was theninserted into the heat shrink tubing outer sheath so that the innerelements were aligned for capture in the heat shrink tubing. At theproximal end of the microcannula assembly, the two communicatingelements were extended outside of the heat shrink tubing and separated.

The assembly was placed in a hot air stream at 220-240 degrees F., sothe heat shrink recovered and the inner elements were captured to form amulti-component shaft of the microcannula. The composite microcannulademonstrated a final outer dimension of 200 to 230 microns with a lumenof 75 microns. To finish the assembly, extension communicating elementswere bonded to the proximal end of the two communicating elementsrespectively. The extensions were finished by adding a Luer infusionconnector and an optical connector to serve as interfaces to thecommunicating elements. Testing of the completed microcannula wasperformed, demonstrating simultaneous fluid delivery from the Luerconnector and light delivery from the optical connector to themicrocannula tip.

Example 2

The microcannula fabricated in Example 1 was tested in accessingSchlemm's Canal of an enucleated human eye. The first communicatingelement, the infusion lumen, was attached to a syringe filled with fluidat the proximal Luer connection. The second communicating element, theoptical fiber, was attached to a light emitting source at the proximalconnection. Operating at the temporal-superior segment of the anteriorportion of the eye, two radial incisions were made to a depth ofSchlemm's Canal and extending from the clear cornea approximately 3 mmposterior. A third incision was made across the posterior end of theradial incisions to define a surgical flap. The flap was then excised uptoward the limbus, exposing Schlemm's Canal. The distal tip of thecomposite microcannula was inserted into Schlemm's Canal. The lightsource for the second communicating element was activated and themicrocannula was advanced along Schlemm's Canal. The light emitting fromthe microcannula tip was seen through the sclera and used to help guidethe microcannula. The microcannula was advanced along Schlemm's Canaluntil the tip was seen reaching an appropriate location. The syringeconnected to the first communicating element extension was used toinject fluid (Healon GV, Advanced Medical Optics, Inc.) into Schlemm'sCanal as needed to aid microcannula advancement. After the desiredmicrocannula positioning was completed, the microcannula wasrepositioned for additional fluid injections and subsequently completelyretracted from Schlemm's Canal.

Example 3

In the following example, an atraumatic rounded distal tip component wasfabricated for placement over a composite microcannula. Polyethyleneteraphthalate (PET) shrink tubing (Advanced Polymers, Nashua N.H.) 0.008inch ID and 0.00025 inch wall thickness was obtained. A length of shrinktubing approximately 2 cm long was placed over a mandrel comprised of asection of hypodermic tubing 0.003 inch×0.007 inch diameter. Tefloncoated steel wire, 0.0025 inch diameter was held inside the hypodermictubing and extending beyond the end of the shrink tubing. Understereomicroscope visualization, a point heat source (adjustablesoldering iron) set to 500 degrees C. was brought into close proximityto the end of the heat shrink tubing. The heat was allowed to melt theend of the tube without touching the heat source to the polymer. Thesurface tension of the polymer melt created a rounded “ball-end” tipwith a 0.0025 inch diameter lumen. The polymer was allowed to cool andthen stripped off of the mandrel and wire. The length of PET shrinktubing held beyond the end of the mandrel determined the final diameterof the rounded tip. Approximately 0.08 inches of extension yielded tipsapproximately 0.008 inch or 200 micron outer diameter.

The finished component was then drawn over the distal end of a compositemicrocannula similar to Example 1, which was 0.0075 inches or 190microns in largest diameter. The tip component was butted up to the endof the composite elements and then shrunk in place with a hot air streamat 240 degrees F. to attach the tip.

Example 4

In the following example, the body of a composite microcannula wasformed out of a wire coil and polymer heat shrink tubing. The coil wasfabricated by progressively winding a 0.003 inch by 0.001 inch stainlesssteel ribbon under 20 grams tension around a 0.0055 inch diameterstainless steel mandrel. Following removal from the mandrel, theresulting wire ribbon coil had an outside diameter of 0.008 inches or200 microns, an inside diameter of 0.006 inches or 150 microns, andoverall length of approximately 5 inches. A 6 inches long piece of 0.010inch or 250 micron ID PET heat shrink with a preformed rounded tip atone end was slipped over the coil and recovered using hot air over theentire length of the coil. A 0.004 inch diameter optical fiber was thenloaded into the lumen of the microcannula and advanced to the distalend. The proximal ends were terminated into a fluid infusion lumen and0.5 mm diameter optical fiber respectively. The distal portion of theassembly was found to have desirable mechanical characteristics offlexibility and resistance to kinking.

Example 5

An experiment was performed to test the coil-wound microcannula designas described in Example 3. Whole globe human eyes were obtained from atissue bank. The enucleated eyes were prepared by first injecting thevitreous chamber with phosphate buffered saline to replace fluid lostpost-mortem and bring the globes to a natural tone. Operating at thetemporal-superior segment of the anterior portion of the eye, two radialincisions were made to a depth of Schlemm's Canal and extending from theclear cornea approximately 3 mm posterior. A third incision was madeacross the posterior end of the radial incisions to define a surgicalflap. The flap was then excised up toward the limbus, exposing Schlemm'sCanal. The microcannula was inserted into Schlemm's Canal and advancedto approximately 90 degrees around from the access site. The metal coilwas able to be seen through the scleral wall allowing the amount ofmicrocannula advancement to be determined.

Example 6

In the following example, a composite microcannula with severalcommunicating elements in parallel alignment forming a distal segmentwith a maximum outer diameter of 250 microns was fabricated. The outermember comprised a tubular structure and the two internal communicatingelements comprised elongated linear elements. At the distal end of theouter structure, an atraumatic spherical-shaped distal tip was formed. Acommunicating lumen was formed in the annular space between the outertube and the inner members. The inner members comprised an optical fiberand a reinforcement element. The outer member was a tubular structurecomprised of three sizes of PEBAX (polyamide/polyether copolymer), 63durometer tubing:

1) Proximal Section 0.016 inch ID×0.026 inch OD, 24 inch length

2) Mid Section 0.010 inch ID×0.014 inch OD, 4 inch length

3) Distal Section 0.006 inch ID×0.008 inch OD, 1.8 inch length

The outer tubular element was constructed by first cutting theindividual shaft segments to lengths appropriate for setting the finaloverall length of the microcannula. The mid section was inserted intothe proximal section with appropriate length for an overlapping bond.The tubular elements were then bonded together with an adhesive or bymelt-fusing the polymeric tubes together with a controlled heat process.The distal section was bonded to the mid shaft similarly. These tubeswere bonded together to form a decreasing outer diameter toward thedistal tip.

The reinforcement element comprised 304 Stainless Steel wire size0.0010+/−0.0005 inch OD, and the optical fiber comprised a plasticoptical fiber fabricated from polystyrene and polymethylmethacrylatewith an 85 to 100 micron OD. The reinforcement element and the opticalfiber were cut to lengths appropriate for setting the final overalllength of the microcannula. The reinforcement element and optical fiberwere inserted into the outer member assembly. The inner elements werealigned with the distal tip of the distal shaft.

An atraumatic rounded tip was formed at the end of the distal section. Aquick drying UV curable adhesive (Loctite Brand 4305) was applied to theouter section of the distal tip. An adhesive of medium to high viscositywas chosen so that the adhesive application formed a bulbous structureapproximately 0.001 inch thickness. A small, approximately 0.03microliter amount of adhesive was used to create the tip. The adhesivewas cured to form the spherically shaped atraumatic tip with a diameterof 0.010 inches or 250 microns.

The free end of the infusion lumen was terminated with a female Luerport. The proximal end of the optical fiber was connected to a PlasticOptical Fiber (POF) that terminated in an optical SMA connector.

The area of the microcannula assembly where the optical fiber andreinforcement enter the inside of the outer member was sheathed in aprotective plastic housing forming a hub. The hub also provided a meansfor manipulation of the microcannula.

The optical SMA termination was connected to a light source and lightwas conducted to the tip of the microcannula to provide a signal beacon.The Luer termination was connected to a fluid-filled syringe andactivation of the syringe resulted in fluid delivery through themicrocannula exiting from the distal tip. Delivery of the signal beaconlight and fluid could be activated individually or simultaneously.

Example 7

In the following example, a composite microcannula with severalcommunicating elements in parallel alignment forming a distal segmentwith a maximum outer diameter of 350 microns was fabricated similarly toExample 6. In this embodiment the outer member was constructed withthree sizes of PEBAX tubing with slightly larger dimensions:

1) Proximal Section 0.016 inch ID×0.026 inch OD, 24 inch length

2) Mid Section 0.0130 inch ID×0.015 inch OD, 4 inch length

3) Distal Section 0.008 inch ID×0.012 inch OD, 1.8 inch length

A spherically shaped atraumatic tip was fabricated on the microcannulaby the method described in Example 6, forming a distal tip with adiameter of 0.014 inches or 350 microns. In this embodiment, noreinforcing element was placed into this cannula construction, however aplastic optical fiber was incorporated similar to Example 6.

The optical SMA termination was connected to a light source and lightwas conducted to the tip of the microcannula. The Luer termination wasconnected to a fluid-filled syringe and activation of the syringeresulted in fluid delivery through the microcannula exiting from thedistal tip.

Example 8

The composite microcannulae of Example 6 and Example 7 were tested inhuman eyes similarly to the method of Example 2. The distal tip anddistal segments of the microcannulae could be advanced along the entirecircumference of Schlemm's Canal for 360 degrees while observing thebeacon signal at the microcannula tip through the sclera. Injection ofsmall amounts of hyaluronic acid-based surgical viscoelastic fluid(Healon GV, Advanced Medical Optics Inc.) delivered during advancementof the microcannulae decreased the force required for advancement andprovided for more progressive advancement.

Example 9

A composite microcannula with several collinear elements was fabricatedsimilar to Example 6. In this embodiment, the outer structure had no midsection in that the proximal section was connected directly to thedistal section.

Example 10

In order to determine the optimal flexural properties of a compositemicrocannula for introduction into small tissue spaces, a family ofmicrocannulae were fabricated with the same outer dimensions andmaterial characteristics but with varying flexural rigidity. Flexuralrigidity of a body is equal to the product of the flexural modulus, E,and the moment of inertia of the cross-section, I, and is typicallycalled EI. The outer sheath comprised PEBAX tubing with 0.008 inch (200micron) OD and 0.006 inch (150 micron) ID. The sample set comprised thetubing alone without reinforcing element(s), the tubing with a 100micron outer diameter plastic optical fiber placed within the lumen andthe tubing with stainless steel reinforcing wires of varying size in thelumen. The ends of the components were secured with adhesive, whileforming an atraumatic spherically shaped tip, as described in Example 6.The lumen allowed fluid delivery to the tip of the microcannula from aproximally attached Luer connector.

The flexural rigidity of the microcannulae were evaluated by mechanicaltesting. The microcannulae cantilever force-displacement characteristicswere tested on a mechanical testing apparatus with a high sensitivityload cell (Instron model 5542, 5N Load Cell). The linear region of theresultant data was used to calculate the measured flexural rigidity ofthe test samples. Measured Flexural Rigidity Microcannula Description(EI) [kN*m^(2]) PEBAX Outer Sheath 3.09E−11 PEBAX Outer Sheath with0.001 in 3.76E−11 diameter SS wire PEBAX Outer Sheath with 100 micron6.33E−11 diameter plastic optical fiber PEBAX Outer Sheath with 0.002 in9.69E−11 diameter SS wire PEBAX Outer Sheath with 0.003 in 2.86E−10diameter SS wire PEBAX Outer Sheath with 0.004 in  7.5E−10 diameter SSwire

Example 11

The microcannulae fabricated in Example 10 were tested for the abilityto access Schlemm's Canal of a human eye similar to the methodsdescribed in Example 2. In a first trial, the distal tip of themicrocannulae were inserted into the Canal and advanced without deliveryof fluid from the microcannula tip. The number of degrees of advancementaround the eye was recorded for each microcannula. In the next trial,the test was repeated with the delivery of a small amount ofviscoelastic fluid (Healon GV, Advanced Medical Optics Inc.) from themicrocannula tip during advancement. One property of Healon GV, ahyaluronic acid based viscoelastic fluid, is very high lubricity. Threeeyes were used for the evaluation, with cannulations performed bothclockwise and counterclockwise from the surgical access site.

When tested for the degree of advancement within Schlemm's Canal, themicrocannulae with low flexural rigidity could be slowly advanced alongCanal until further advancement was no longer possible due to lack offorce transfer. These lower flexural rigidity devices tended to bend orkink when reaching the limit of travel. The microcannulae with very highflexural rigidity could be advanced a short distance until furtheradvancement was no longer possible due to the inability of themicrocannula to bend with the curve of Schlemm's Canal. If advancedfurther, the microcannula with very high flexural rigidity in some casespunctured through the outer wall of the Canal, an undesirable result.The testing was performed by advancing each device manually, attemptingto use a comparable maximum force for each test run, so as to maintainan adequate comparison. In cases where the cannula did not traverse thefull extent of the Canal, the force required to advance the cannulaincreased with increased extent of cannulation, which was attributed tointeraction of the compliance properties of the device and thefrictional forces between the device and the tissues of the Canal.Degrees Degrees Degrees Degrees Cannulation Cannulation CannulationCannulation Microcannula Achieved - Achieved - Achieved - Achieved -Flexural No Fluid No Fluid Fluid Fluid Rigidity (EI) Delivery DeliveryDelivery Delivery [kN*m²] AVG Std Dev AVG Std Dev 3.09E−11 183 64 360 03.76E−11 242 35 360 0 6.33E−11 265 78 360 0 9.69E−11 203 23 360 02.86E−10 177 25 360 0  7.5E−10 80 20 89 26

The results of advancing the microcannulae into Schlemm's Canal withoutfluid delivery demonstrated an optimal flexural rigidity ofapproximately 6.33 E-11 kN*m². Flexural rigidity in the range of 3.09E-11 to 2.86 E-10 provided a microcannula that was able to accessapproximately 180 degrees of the eye. Such properties would allow theentire eye to be accessed from a single surgical site by advancing themicrocannula in both directions.

The results of advancing the microcannula into Schlemm's Canal withfluid delivery demonstrated improved performance except for themicrocannula with the highest flexural rigidity. Flexural rigidity inthe range of 3.09 E-11 to 2.86 E-10 kN*m² coupled with the delivery of alubricious material (Healon GV) allowed the entire circumference ofSchlemm's Canal (360 degrees) to be accessed by the test microcannulae.It was noted that the amount of force required to advance each devicewas significantly decreased by the presence of the lubricious fluidbeing delivered from the distal tip of the microcannula during thecannulation. In addition, a number of attempts to advance a microcannulainto Schlemm's Canal without fluid delivery were made by depositing asmall amount of the viscoelastic fluid at the surgical site and thenpassing the cannula through the gel. These did not result in anysignificant decrease in force or increase in advancement of the testdevices, indicating the advantage of delivering fluid at themicrocannula tip during manipulation and advancement.

Many features have been listed with particular configurations, options,and embodiments. Any one or more of the features described may be addedto or combined with any of the other embodiments or other standarddevices to create alternate combinations and embodiments.

The preferred embodiments described herein are illustrative only, andalthough the examples given include many specifics, they areillustrative of only a few possible embodiments of the invention. Otherembodiments and modifications will no doubt occur to those skilled inthe art. The examples given should only be interpreted as illustrationsof some of the preferred embodiments of the invention.

1. A composite microcannula for access and advancement into a tissuespace of the eye comprising: at least one flexible, tubularcommunicating element configured to fit within the tissue space andhaving a proximal end and a distal end; a proximal connector attached tosaid proximal end, said proximal connector configured for introductionof materials, energy or tools; and a reinforcing member connected withthe communicating element, wherein an outer diameter of said compositemicrocannula is no more than 350 microns.
 2. The microcannula of claim1, wherein the composite microcannula has a flexural rigidity in therange of 3.09 E-11 to 2.86 E-10 kN*m².
 3. The microcannula of claim 1,wherein the reinforcing member provides greater axial and flexuralstiffness at the proximal end of the microcannula as compared to thedistal end of the microcannula.
 4. The microcannula of claim 1, whereinthe reinforcing element is malleable to allow manual shaping of themicrocannula.
 5. The microcannula of claim 1, wherein the reinforcingelement comprises a metal.
 6. The microcannula of claim 1, wherein thecommunicating element comprises a flexible polymer and the reinforcingmember comprises a metal.
 7. The microcannula of claim 1, wherein themicrocannula comprises a signal beacon capable of identifying a positionof the distal tip.
 8. The microcannula of claim 1, wherein themicrocannula further comprises at least one additional communicatingelement.
 9. The microcannula of claim 8, wherein one of thecommunicating elements provides a signal beacon at the microcannuladistal tip.
 10. The microcannula of claim 8, wherein the additionalcommunicating element is located within a lumen of the firstcommunicating element.
 11. The microcannula of claim 10, wherein thecommunicating elements are in concentric alignment.
 12. The microcannulaof claim 8, wherein the communicating elements are in parallel alignment13. The microcannula of claim 1, wherein the microcannula comprises twoor more reinforcing elements.
 14. The microcannula of claim 1, whereinthe reinforcing element comprises a coil.
 15. The microcannula of claim1, wherein the reinforcing element is tapered toward the distal end ofthe microcannula.
 16. The microcannula of claim 1, wherein thecommunicating element includes a segment chosen from the groupconsisting of a segment of tubing, a segment of optical fiber and asegment of an electrical conductor.
 17. The microcannula of claim 1,wherein the microcannula is configured to fit within a tissue spaceselected from the group consisting of Schlemm's Canal, an aqueouscollector channel, an aqueous vein, a suprachoroidal space and a retinalblood vessel of the eye.
 18. The microcannula of claim 1, wherein thedistal end has a rounded distal tip.
 19. The microcannula of claim 18,wherein the communicating element comprises an optical fiber capable ofdelivering light to the rounded tip and wherein, when light is deliveredto said rounded tip, said rounded tip acts to disperse the light forimproved off-axis visualization.
 20. The microcannula of claim 1,wherein the communicating element and the reinforcing element are joinedby an outer sheath.
 21. The microcannula of claim 20, wherein the outersheath comprises heat shrink tubing.
 22. The microcannula of claim 1,wherein the communicating element and the reinforcing element are joinedwith an adhesive.
 23. The microcannula of claim 1, additionallycomprising a lubricious outer coating.
 24. A composite microcannula foraccess and advancement into a tissue space of the eye comprising: atleast one flexible, tubular communicating element having a proximal end,a distal end, and a fluid communicating lumen, a proximal connectorconfigured for delivery of fluid, a signal beacon, and a secondcommunicating element configured to deliver the signal beacon, thesignal beacon being capable of identifying the microcannula distal tip,wherein an outer diameter of said composite microcannula is no more than350 microns.
 25. The composite microcannula of claim 24, wherein thesecond communicating element comprises an optical fiber and the signalbeacon delivers visible light.
 26. The microcannula of claim 24, whereinthe composite microcannula has a flexural rigidity in the range of 3.09E-11 to 2.86 E-10 kN*m².
 27. The composite microcannula of claim 24,additionally comprising a rounded distal tip.
 28. The compositemicrocannula of claim 27, wherein the rounded distal tip acts todisperse the signal beacon for improved off-axis visualization.
 29. Acomposite microcannula for access and advancement into a tissue space ofthe eye comprising: a flexible, tubular communicating element configuredto fit within the tissue space, the communicating element having aproximal end and a distal end; a proximal connector attached to saidproximal end, said proximal connector configured for introduction ofmaterials, energy or tools; a second communicating element comprising anoptical fiber; and a rounded distal tip forming the distal end of themicrocannula, wherein the microcannula is configured such that light isdelivered through the optical fiber proximal to the rounded tip todisperse light at the distal tip to improve off-axis visualization andidentification of the tip location within a tissue space of the eye. 30.The microcannula of claim 29, wherein the microcannula additionallycomprises a reinforcing member connected with the communicating element.31. The microcannula of claim 29, wherein the microcannula has an outerdiameter of not more than 350 microns.